Install Aardvark Post-IT theme with the patch
Move block to new block region at the top
Move block from the new region (it becomes empty) - make sure that side block regions are not getting hidden at this point.
Also, testing existing functionality is required:
Move all blocks from left or right region that does not contain block adding block.
On the last block move, the region should be hidden.
Move any block towards the hidden region, the region should be displayed and accept new block.